The present invention is directed to a particle beam apparatus comprising a particle beam source, at least one condenser lens, a line-shaped subject and an imaging lens for imaging the line-shaped subject onto an image surface.
A particle beam apparatus having a particle beam source, at least one condenser lens, a line-shaped subject and imaging lens for imaging the line shaped subject onto an image surface are used for lithographic production of microstructures and such an apparatus is disclosed in copending U.S. Pat. application Ser. No. 824,237, which was filed Jan. 30, 1986, and now U.S. Pat. No. 4,724,328, whose disclosure is incorporated by reference thereto and was based on German Patent Application No. 35 04 714. The line-shaped subject is thereby composed of a line-shaped multi-perforation aperture diaphragm inserted into the beam path of the particle beam source and this aperture serves to generate a plurality of particle beam probes. The latter impinge on the surface of a body covered with a photoresist layer, particularly a semiconductor body, that is to be structured, and the photoresist layer is exposed in the respective points of incidence.
However, in such an imaging of a line-shaped subject onto a surface, particularly onto the surface of a semiconductor body to be structured, disturbing distortions will occur. For example, although the multi-perforation structure of the aperture diaphragm will have a fixed spacing between perforations, the image spots produced and exposed by the plurality of particle beam probes are not equal distance from one another and will lie farther and farther apart with increasing distance from the optical axis of the particle beam apparatus and will also have larger and larger image spot dimensions (isotropic distortion). In addition, unlike a straight line of perforations in the aperture diaphragm, the image spots will, likewise, not lie on a straight line, but instead will be arranged on an S-shaped curve, which is referred to as anisotropic distortion. Deviations in the shape of the image spot in comparison to the shape of the perforations in the aperture diaphragm generating the particle beam probes also occur due to these distortions.